<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id='showtime'>
    showtime:
</div>

<script>
    var t = null;
    t = setTimeout(time, 1000);//開始运行
    function time() {
        clearTimeout(t);//清除定时器
        dt = new Date();
        var y = dt.getFullYear();
        var mt = dt.getMonth() + 1;
        var day = dt.getDate();
        var h = dt.getHours();//获取时
        var m = dt.getMinutes();//获取分
        var s = dt.getSeconds();//获取秒
        document.querySelector(".showTime").innerHTML = '当前时间：' + y + "年" + mt + "月" + day + "-" + h + "时" + m + "分" + s + "秒";
        t = setTimeout(time, 1000); //设定定时器，循环运行
    }
</script>
</body>

</html>